1. Field of the Invention
The present invention relates to a method and apparatus for cleaning the porous ceramic grind chuck used in semiconductor wafer grinding machines.
2. Background of the Invention
U.S. Pat. No. 7,118,446, issued to Thomas A. Walsh and Salman Kassir and assigned to the assignee of the present invention exemplifies the status of prior art grinder apparatus technology. A chuck is provided in the apparatus to hold a work piece, such as a wafer, in place so that the work piece does not slip or otherwise move while being shaped by a grind wheel.
The chuck is porous i.e. holes are drilled therethrough it or otherwise comprises a porous material; a partial vacuum being provided below the chuck to hold the work piece in place. Coolant is pumped directly onto an area of contact between a grind wheel and the workpiece surface, providing cooling and cleaning of grind debris (swarf) from the surface of the workpiece.
During the grinding process, vacuum is applied through the porous portion of the work chuck to hold the wafer. Due to dimensional differences between the wafer and the porous portion of the work chuck, there can be a small section near the periphery of the porous portion that is exposed to the grinding swarf. The porous portion of the work chuck will “suck-up” the small particles in the grind swarf. Over time, the small particles from the grind swarf will clog the porous material closest to the perimeter of the wafer. The porous material may get clogged with small particles below the wafer surface. If the wafer edge is not pulled down to the work chuck, the edge of the wafer will rise during the grinding process removing too much material at the edge of the wafer. The clogging of the work chuck edge reduces the life of the work chuck due to the over grinding of the wafer edge.
What is thus desired is to provide a work chuck cleaning procedure wherein the cleaning can be done either automatically or manually.